package com.wc.AlgoOJ_homework.AlgoOJ_test6.E_最大互质索引;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.StringTokenizer;

/**
 * @Author congge
 * @Date 2024/3/22 19:49
 * @description http://43.138.190.70:8888/p/734?tid=65f90101f9a80dc9ddc3f0c4
 */
public class Main {
    static FastReader sc = new FastReader();
    static PrintWriter out = new PrintWriter(System.out);
    static int N = 200010;
    static int[] a = new int[N];
    static int[] lastIdx = new int[1001];
    static int t, n;

    public static void main(String[] args) {
        t = sc.nextInt();
        while (t-- > 0) {
            n = sc.nextInt();
            Arrays.fill(lastIdx, 0);
            for (int i = 1; i <= n; i++) a[i] = sc.nextInt();
            for (int i = 1; i <= n; i++) {
                lastIdx[a[i]] = i;
            }
            int maxV = -1;
            for (int i = 1; i <= 1000; i++) {
                for (int j = 1; j <= 1000; j++) {
                    if (lastIdx[i] != 0 && lastIdx[j] != 0) {
                        if (gcd(i, j) == 1) {
                            maxV = Math.max(maxV, lastIdx[i] + lastIdx[j]);
                        }
                    }
                }
            }
            out.println(maxV);
        }
        out.flush();
    }

    static int gcd(int a, int b) {
        if (a > b) return gcd(b, a);
        while (b % a != 0) {
            int tmp = b % a;
            b = a;
            a = tmp;
        }
        return a;
    }
}

class FastReader {
    StringTokenizer st;
    BufferedReader br;

    FastReader() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    String nextLine() {
        String s = "";
        try {
            s = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return s;
    }

    long nextLong() {
        return Long.parseLong(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }

    // 是否由下一个
    boolean hasNext() {
        while (st == null || !st.hasMoreTokens()) {
            try {
                String line = br.readLine();
                if (line == null)
                    return false;
                st = new StringTokenizer(line);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return true;
    }
}
